JP2015083377A - Thermoformed container and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoformed container being excellent in appearance due to suppression of defect occurrence and coloration in melt molding, and having sufficient strength.SOLUTION: The present invention is a thermoformed container comprising an EVOH layer (A) with an ethylene-vinyl alcohol copolymer (I) being as a main component, where the EVOH layer (A) contains an unsaturated aldehyde (II) and the content of the unsaturated aldehyde (II) in the EVOH layer (A) is 0.01 ppm or more and 100 ppm or less. The unsaturated aldehyde (II) is desirably an unsaturated aliphatic aldehyde. The unsaturated aliphatic aldehyde is desirably crotonaldehyde, 2,4-hexadienal, 2,4,6-octatrienal or a combination thereof. The EVOH layer (A) desirably further contains a conjugated polyene compound (III). The content of the conjugated polyene compound (III) in the EVOH layer (A) is preferably 0.01 ppm or more and 1,000 ppm or less.

Description

  The present invention relates to a thermoformed container and a method for producing the same.

  An ethylene-vinyl alcohol copolymer (hereinafter sometimes abbreviated as “EVOH”) is widely used as a material that can be melt-molded and has excellent gas barrier properties. For example, EVOH is used as a material for films and sheets formed by melt molding. The EVOH layer made of this sheet or the like is used as a packaging material by being laminated with a thermoplastic resin layer mainly composed of an olefin resin or the like. A packaging material including such an EVOH layer is used as a packaging container by thermoforming. Such a packaging container is excellent in oxygen barrier properties by including an EVOH layer, and therefore is widely used in various fields such as foods, cosmetics, medicinal chemicals, and toiletries where oxygen barrier properties are required.

  However, the EVOH layer generally lacks thermoformability as compared with a thermoplastic resin layer mainly composed of an olefin resin or the like. For this reason, the packaging material including the EVOH layer is likely to have defects such as pinholes and cracks during thermoforming, and the packaging container is likely to have a poor appearance. Further, since the packaging material including the EVOH layer is likely to have thickness unevenness after thermoforming, there is a tendency to cause problems such as a gas barrier property of the packaging container and a decrease in mechanical strength.

  In order to improve such a problem, a plasticizer is added to a resin composition for forming a sheet or the like mainly composed of EVOH (Japanese Patent Laid-Open Nos. 53-088067 and 59-020345). Reference), blending polyamide (see JP-A No. 52-141785) and the like have been studied.

  As a method for producing EVOH, a method is known in which crotonaldehyde is coexisted in addition to ethylene and vinyl acetate in the EVOH polymerization step (see JP 2007-31725 A). According to this production method, scale adhesion inside the polymerization can can be suppressed by allowing crotonaldehyde to coexist during the polymerization. As a result, the EVOH film obtained by this manufacturing method is said to be able to reduce the generation of fish eyes caused by scale contamination.

  However, the crotonaldehyde added during the polymerization is partially consumed in the polymerization process and the saponification process. Crotonaldehyde has a high solubility in water of 18.1 g / 100 g (20 ° C.) (The MERCK INDEX 14th 2006). On the other hand, the EVOH production method usually includes a step of washing with water sodium acetate produced by neutralization after saponification. Therefore, crotonaldehyde added at the time of polymerization is almost completely removed in the water washing step at the time of EVOH production, and hardly remains in products such as EVOH films. Therefore, in the production method described above, the effects of adding an unsaturated aldehyde such as improvement in thermal stability and long-term operation characteristics (long run property) in thermoforming are unknown.

JP 53-088067 A JP 59-020345 A JP-A-52-141785 JP 2007-31725 A

  An object of the present invention is to provide a thermoformed container having excellent appearance and sufficient strength by suppressing generation of defects and coloring in melt molding. Moreover, an object of this invention is to provide the manufacturing method which can provide the thermoforming container which has such a characteristic, and is excellent in long run property (viscosity stability).

  The invention made to solve the above problems is a thermoformed container comprising an EVOH layer (A) mainly composed of an ethylene-vinyl alcohol copolymer (I), wherein the EVOH layer (A) is unsaturated. It is a thermoformed container containing aldehyde (II) and having a content of unsaturated aldehyde (II) in the EVOH layer (A) of 0.01 ppm to 100 ppm.

  The thermoformed container of the present invention includes an EVOH layer (A) in which the content of unsaturated aldehyde (II) is in a specific range. The EVOH layer (A) is formed, for example, by melt molding a resin composition containing EVOH as a main component and containing a specific amount of unsaturated aldehyde (II). In this melt molding, since the resin composition contains a specific amount of unsaturated aldehyde (II), the effect is not clear, but the occurrence of defects such as gelled streaks and streaks, fine pinholes and cracks Generation and coloring can be suppressed. As a result, the EVOH layer (A) obtained from the resin composition, and thus the thermoformed container including the EVOH layer (A), has excellent appearance and sufficient strength. Moreover, when EVOH layer (A) contains a specific amount of unsaturated aldehyde (II), it is excellent in the self-purge property in the manufacturing process of a thermoformed container, and can reduce the manufacturing cost of the thermoformed container.

  In addition, although the effect | action of unsaturated aldehyde (II) which suppresses generation | occurrence | production of defects, such as a streak, and coloring in the melt-molded article (EVOH layer (A) film etc.) using the said resin composition is not necessarily clear. It is presumed that the oxidative deterioration of EVOH (I) during melt molding is prevented by oxidation of unsaturated aldehyde (II). Such an antioxidant effect of EVOH (I) is considered to suppress the generation of heat-degraded products such as gel-like material.

  The unsaturated aldehyde (II) is preferably an unsaturated aliphatic aldehyde. As this unsaturated aliphatic aldehyde, crotonaldehyde, 2,4-hexadienal, 2,4,6-octatrienal or a combination thereof is preferable. In the thermoformed container, the EVOH layer (A) contains the specific substance as the unsaturated aldehyde (II), so that the appearance is superior and the strength is sufficient.

  The EVOH layer (A) may further contain a conjugated polyene compound (III). The content of the conjugated polyene compound (III) in the EVOH layer (A) is preferably 0.01 ppm or more and 1,000 ppm or less. In the EVOH layer (A) further containing a specific amount of the conjugated polyene compound (III), the oxidative deterioration during melt molding of the EVOH layer (A) is suppressed by the conjugated polyene compound (III). Occurrence of defects such as defects, coloring, and the like are further reduced, and the appearance is further improved. Therefore, the said thermoformed container is equipped with the EVOH layer (A) further containing a specific amount of the conjugated polyene compound (III), so that the occurrence of defects is further reduced and the appearance is further improved. Moreover, since it is more excellent in the self purge property when forming the EVOH layer (A) by melt molding, the manufacturing cost of the thermoformed container can be further reduced.

  The conjugated polyene compound (III) is preferably sorbic acid, sorbate or a combination thereof. The EVOH layer (A) further containing sorbic acid or the like as the conjugated polyene compound (III) has a gel-like shape because the oxidative deterioration during melt molding of the EVOH layer (A) is effectively suppressed by sorbic acid or the like. The occurrence of defects such as blisters, coloring, and the like are further reduced, and the appearance is further improved. Therefore, the said thermoformed container is equipped with the EVOH layer (A) further containing a specific amount of the conjugated polyene compound (III), so that the occurrence of defects is further reduced and the appearance is further improved. Moreover, since it is further excellent in the self purge property when forming the EVOH layer (A) by melt molding, the manufacturing cost of the thermoformed container can be further reduced.

The thermoforming container includes a thermoplastic resin layer (B) laminated on one surface side and the other surface side of the EVOH layer (A), and the EVOH layer (A) and the thermoplastic resin layer (B And a polyolefin layer (C) mainly composed of a carboxylic acid-modified polyolefin. The solubility parameter (SP value) of the thermoplastic resin constituting the thermoplastic resin layer (B) calculated from the Fedors equation is preferably 11 (cal / cm ³ ) ^1/2 or less. By further including such SP value thermoplastic resin layer (B) and polyolefin layer (C), it is possible to improve gas shielding properties, oil resistance, impact resistance and the like under high humidity.

  The thermoformed container is preferably a cup-shaped container or a tray-shaped container. That is, the thermoformed container can be suitably used for a cup-shaped container or a tray-shaped container that requires gas barrier properties, and also has excellent appearance.

  The present invention includes a step of forming an EVOH layer (A) using a resin composition containing ethylene-vinyl alcohol copolymer (I) as a main component and the unsaturated aldehyde (II), and the EVOH layer. And a step of thermoforming a layer containing (A), and a method for producing a thermoformed container in which the content of the unsaturated aldehyde (II) in the resin composition is 0.01 ppm or more and 100 ppm or less.

  According to the method for producing a thermoformed container, EVOH containing a specific amount of unsaturated aldehyde (II) can be suppressed while the generation of defects such as gelled blisters and streaks during the formation of the EVOH layer (A) and coloring can be suppressed. Layer (A) is obtained. Therefore, the thermoformed container obtained by the manufacturing method is excellent in appearance and has sufficient strength. Moreover, it is excellent in the self purge property in the manufacturing process of a thermoformed container, and can reduce manufacturing cost because the said resin composition and EVOH layer (A) contain a specific amount of unsaturated aldehyde (II). In addition, since the production method uses a resin composition containing a specific amount of unsaturated aldehyde (II), the oxidation of EVOH is prevented and the long-run property (viscosity stability) is excellent.

Here, the “main component” is a component having the highest content, for example, a component having a content of 50% by mass or more. “Ppm” means the mass ratio of the corresponding component in the layer constituting the thermoformed container, and 1 ppm is 0.0001 mass%. The “solubility parameter calculated from the Fedors equation” is an SP value calculated from the following equation.
SP value δ = (E / V) ^1/2
E: Molecular aggregation energy (cal / mol), which is determined as the sum of evaporation energy of atoms or atomic groups constituting the compound.
V: Molecular volume (cm ³ / mol), which is determined as the sum of the molar volumes of atoms or atomic groups constituting the compound.

  The thermoforming container of the present invention contains a specific amount of unsaturated aldehyde (II) in the EVOH layer (A), thereby suppressing the occurrence of defects such as gelled blisters and streaks due to melt molding and coloring. Excellent in strength and sufficient strength. Furthermore, since the EVOH layer (A) contains a specific amount of unsaturated aldehyde (II), the thermoformed container is excellent in self-purge property in the manufacturing process, and the manufacturing cost of the thermoformed container can be reduced. it can. Therefore, the thermoformed container can be used for various applications. Since the production method of the present invention uses a resin composition containing a specific amount of unsaturated aldehyde (II), the oxidation of EVOH is prevented and the long-run property (viscosity stability) is excellent.

It is a typical perspective view which shows the cup-shaped container which is one Embodiment of the thermoforming container of this invention. It is sectional drawing of the cup-shaped container of FIG. It is typical sectional drawing which shows the principal part of the cup-shaped container of FIG. It is a schematic diagram for demonstrating the manufacturing method of the cup-shaped container of FIG. It is a schematic diagram for demonstrating the manufacturing method of the cup-shaped container of FIG.

  Hereinafter, an embodiment of a thermoformed container and a method for producing the same according to the present invention will be described. However, the present invention is not limited to the embodiments described below.

<Thermoforming container>
The thermoformed container of the present invention is used in various fields such as food, cosmetics, medicinal chemicals, and toiletries where oxygen barrier properties are required. This thermoformed container is formed as a container having an accommodating portion by thermoforming a multilayer body, for example.

[Container]
The accommodating portion is a portion that accommodates contents such as food. The shape of this accommodating part is determined corresponding to the shape of the contents. Specifically, the thermoformed container is formed as, for example, a cup-shaped container, a tray-shaped container, a bag-shaped container, a bottle-shaped container, a pouch-shaped container, or the like.

  The form of the accommodating part can be expressed by a drawing ratio (S) as one index. Here, the drawing ratio (S) is a value obtained by dividing the depth of the deepest part of the container by the diameter of the largest circle inscribed in the opening of the container. That is, the drawing ratio (S) means that the larger the value is, the deeper the container is, and the smaller the value is, the shallower the container is. For example, when the thermoformed container is cup-shaped, the drawing ratio (S) is large, and when it is a tray, the drawing ratio (S) is small. Note that the diameter of the inscribed maximum diameter circle is, for example, a circle diameter when the opening of the accommodating portion is circular, a short diameter (short axis length) when it is an ellipse, and a short diameter when it is a rectangle. The length of the side.

  The drawing ratio (S) varies depending on whether the multilayer body for forming the thermoformed container is a film or a sheet, that is, depending on the thickness of the multilayer body. When the thermoformed container is a film formed by thermoforming, the draw ratio (S) is preferably 0.2 or more, more preferably 0.3 or more, and further preferably 0.4 or more. On the other hand, when the said thermoforming container shape | molds a sheet | seat, as drawing ratio (S), 0.3 or more are preferable, 0.5 or more are more preferable, 0.8 or more are further more preferable. The film means a soft material having a thickness of less than 0.2 mm, and the sheet means a material having a thickness larger than that of the film, for example, a soft material having a thickness of 0.2 mm or more.

[Multilayer body]
The multilayer body includes an EVOH layer (A) mainly composed of an ethylene-vinyl alcohol copolymer, and another layer is laminated on at least one surface side of one surface and the other surface of the EVOH layer (A). Is. Here, one surface is the inner surface side of the housing portion when the multilayer body is used as a thermoformed container, and the other surface is the outer surface side of the housing portion. This multilayer body may be in the form of a film or in the form of a sheet.

  Thickness ratio (I) of the total thickness I of the other layer laminated on one surface side of the EVOH layer (A) and the total thickness O of the other layer laminated on the other surface side of the EVOH layer (A) As the lower limit of / O), 1/99 is preferable, and 30/70 is more preferable. Moreover, as an upper limit of said I / O, 70/30 is preferable and 55/45 is more preferable. Note that the thickness of all layers or a single layer of the multilayer body is an average value of thicknesses measured by observation with an optical microscope for samples cut from a plurality of locations of the multilayer body using a microtome. It substantially corresponds to the thickness of the layer.

  The lower limit of the overall average thickness of the thermoformed container is preferably 300 μm, more preferably 500 μm, and even more preferably 700 μm. Further, the upper limit of the overall average thickness of the thermoformed container is preferably 10,000 μm, more preferably 8,500 μm, and further preferably 7,000 μm. The total average thickness refers to the thickness of all layers in the housing portion of the thermoformed container, and the measurement method is the same as that for measuring the thickness of all layers of the multilayer body. When the overall average thickness exceeds the above upper limit, the manufacturing cost of the thermoformed container increases. On the other hand, if the overall average thickness is less than the above upper limit, the rigidity cannot be maintained and the thermoformed container may be easily destroyed. Therefore, it is important that the overall average thickness of the thermoformed container is set to a thickness corresponding to the capacity and application.

  Examples of other layers laminated on the EVOH layer (A) include a thermoplastic resin layer (B), a polyolefin layer (C), and a recovery layer (D). Hereinafter, the EVOH layer (A), the thermoplastic resin layer (B), the polyolefin layer (C), and the recovery layer (D) will be described in detail.

<EVOH layer (A)>
The EVOH layer (A) is a layer mainly composed of EVOH (I) and contains unsaturated aldehyde (II). The EVOH layer (A) preferably further contains a conjugated polyene compound (III), and may contain other optional components as long as the effects of the present invention are not impaired. Hereinafter, each component will be described in detail.

[EVOH (I)]
EVOH (I) is a copolymer obtained by saponifying a copolymer of ethylene and vinyl ester. Examples of the vinyl ester include vinyl acetate, vinyl propionate, vinyl pivalate and the like, and vinyl acetate is preferable. These vinyl esters may be used alone or in combination of two or more.

  EVOH (I) may contain other structural units derived from monomers other than ethylene and vinyl ester. Examples of such monomers include vinyl silane compounds and other polymerizable compounds. As a minimum of content of said other structural unit, 0.0002 mol% is preferable with respect to all the structural units of EVOH (I). Moreover, as an upper limit of content of said other structural unit, 0.2 mol% is preferable with respect to all the structural units of EVOH (I).

  Examples of the vinylsilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxyethoxy) silane, and γ-methacryloxypropylmethoxysilane. Among these, vinyltrimethoxysilane and vinyltriethoxysilane are preferable.

Examples of the other polymerizable compounds include unsaturated hydrocarbons such as propylene and butylene;
Unsaturated carboxylic acids such as (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate or esters thereof;
And vinyl pyrrolidone such as N-vinyl pyrrolidone.

  As a minimum of ethylene content of EVOH (I), it is 20 mol% normally, 24 mol% is preferred and 27 mol% is more preferred. Moreover, as an upper limit of ethylene content of EVOH (I), it is 60 mol% normally, 55 mol% is preferable, 45 mol% is more preferable, 42 mol% is further more preferable, and 38 mol% is especially preferable. When the ethylene content is less than the above lower limit, the thermal stability at the time of melt extrusion is lowered and gelation tends to occur, and defects such as streak and fish eye are likely to occur. In particular, if the operation is performed for a long time at a high temperature or at a higher speed than the general melt extrusion conditions, the possibility of gelation increases. On the other hand, when the ethylene content exceeds the above upper limit, gas barrier properties and the like are lowered, and there is a possibility that the advantageous properties possessed by EVOH (I) cannot be sufficiently exhibited.

  The degree of saponification of the structural unit derived from the vinyl ester of EVOH (I) is usually 85% or more, preferably 90% or more, more preferably 98% or more, and further preferably 99% or more. If the degree of saponification is less than 85%, the thermal stability may be insufficient.

  The lower limit of the EVOH (I) content in the EVOH layer (A) is usually 95% by mass, preferably 98% by mass, more preferably 99% by mass, and still more preferably 99.5% by mass. By setting the content of EVOH (I) to the above lower limit or more, the advantageous properties possessed by EVOH (I) can be sufficiently exerted, so that the EVOH layer (A) is excellent in gas shielding properties, oil resistance and the like.

[Unsaturated aldehyde (II)]
Unsaturated aldehyde (II) is an essential component of the EVOH layer (A) of the thermoformed container. By providing the EVOH layer (A) containing the unsaturated aldehyde (II), the thermoforming container can suppress the occurrence of defects such as gelled blisters and streaks due to melt molding, and has excellent appearance. Moreover, since EVOH layer (A) contains the specific amount of unsaturated aldehyde (II), since it is excellent also in the self purge property in the manufacturing process of a thermoformed container, manufacturing cost can be reduced.

Unsaturated aldehyde (II) refers to an aldehyde having a carbon-carbon double bond or triple bond in the molecule. As this unsaturated aldehyde (II), for example,
Acrolein, crotonaldehyde, methacrolein, 2-methylbutenal, 2-hexenal, 2,6-nonadienal, 2,4-hexadienal, 2,4,6-octatrienal, 5-methyl-2-hexenal, cyclopentenyl An aldehyde having a carbon-carbon double bond in the molecule such as an aldehyde or cyclohexenyl aldehyde;
Examples thereof include unsaturated aliphatic aldehydes such as aldehydes having a carbon-carbon triple bond in the molecule such as propioaldehyde, 2-butyn-1-al, and 2-pentyne-1-al.

  Among these, unsaturated aldehyde (II) is preferably an unsaturated aliphatic aldehyde, more preferably an aldehyde having a carbon-carbon double bond in the molecule, crotonaldehyde, 2,4-hexadienal, 2 , 4,6-octatrienal or a combination thereof is more preferable, and among them, crotonaldehyde having a high solubility in water and a boiling point of around 100 ° C. is removed, for example, in a washing step or a drying step, if necessary. Or since it is easy to add a deficiency, it is especially preferable. As carbon number including the aldehyde part of unsaturated aldehyde (II), 3-10 are preferable, 4-8 are more preferable, 4, 6, and 8 are further more preferable.

  In the unsaturated aldehyde (II), part or all of the hydrogen atoms (excluding the hydrogen atom of the aldehyde group) may be substituted with a substituent as long as the effects of the present invention are not impaired. Examples of the substituent include a halogen atom, a hydroxy group, an amino group, an amide group, and a cyano group.

  As a minimum of content of unsaturated aldehyde (II) in EVOH layer (A), it is 0.01 ppm, 0.05 ppm is preferred and 0.1 ppm is more preferred. On the other hand, as an upper limit of content of unsaturated aldehyde (II), it is 100 ppm and 50 ppm is preferable. When the content of the unsaturated aldehyde (II) is less than the above lower limit, it is insufficient to suppress an increase in the occurrence of gelled puncture over time in melt molding. On the other hand, if the content of unsaturated aldehyde (II) exceeds the above upper limit, condensation between unsaturated aldehydes (II) and crosslinking between EVOH and unsaturated aldehyde (II) condensate occur during melt molding, and fish There is a possibility of causing the generation of eyes and stripes, and there is a possibility that the EVOH layer (A) is likely to be colored.

[Conjugated Polyene Compound (III)]
The conjugated polyene compound (III) suppresses oxidative degradation during melt molding. Here, the conjugated polyene compound (III) has a structure in which carbon-carbon double bonds and carbon-carbon single bonds are alternately connected, and the number of carbon-carbon double bonds is 2 or more. It is a compound having a so-called conjugated double bond. The conjugated polyene compound (III) may be a conjugated diene having two conjugated double bonds, a conjugated triene having three, or a conjugated polyene having a larger number. In addition, a plurality of conjugated double bonds may be present in one molecule without being conjugated with each other. For example, a compound having three conjugated triene structures in the same molecule such as tung oil is also included in the conjugated polyene compound (III). The lower limit of the number of conjugated double bonds of the conjugated polyene compound (III) is preferably 7. When the resin composition contains the conjugated polyene compound (III) having 8 or more conjugated double bonds, the possibility of coloring the multilayer body and thus the thermoformed container is increased.

  In addition to the conjugated double bond, the conjugated polyene compound (III) includes a carboxyl group and a salt thereof, a hydroxyl group, an ester group, an ether group, an amino group, an imino group, an amide group, a cyano group, a diazo group, a nitro group, and a sulfone group. And salts thereof, sulfonyl groups, sulfoxide groups, sulfide groups, thiol groups, phosphate groups and salts thereof, and other functional groups such as phenyl groups, halogen atoms, double bonds, and triple bonds.

  The lower limit of the carbon number of the conjugated polyene compound (III) is preferably 4. Moreover, as an upper limit of carbon number of conjugated polyene compound (III), 30 are preferable and 10 is more preferable. As the conjugated polyene compound (III), sorbic acid, sorbic acid ester, sorbate, myrcene and a mixture of two or more thereof are preferable, sorbic acid, sorbate (sodium sorbate, potassium sorbate, etc.) and These mixtures are more preferred. Sorbic acid, sorbate and a mixture thereof are highly effective in suppressing oxidative degradation at high temperatures, and are also widely used industrially as food additives, and thus are preferable from the viewpoint of hygiene and availability.

  The molecular weight of the conjugated polyene compound (III) is usually 1,000 or less, preferably 500 or less, and more preferably 300 or less. When the molecular weight of the conjugated polyene compound (III) exceeds the above upper limit, the dispersion state of the conjugated polyene compound (III) in EVOH (A) is deteriorated, and the appearance after melt molding may be deteriorated.

  As a minimum of content of conjugated polyene compound (III) in EVOH layer (A), 0.01 ppm is preferred, 0.1 ppm is more preferred, 0.5 ppm is still more preferred, and 1 ppm is especially preferred. Moreover, as an upper limit of content of the conjugated polyene compound (III) in EVOH layer (A), 1,000 ppm is preferable, 800 ppm is more preferable, and 500 ppm is further more preferable. If the content of the conjugated polyene compound (III) is less than the lower limit, the effect of suppressing oxidative degradation during melt molding may not be sufficiently obtained. On the other hand, when the content of the conjugated polyene compound (III) exceeds the above upper limit, the gelation of the resin composition for forming the EVOH layer (A) may be promoted.

[Other optional ingredients]
The EVOH layer (A) includes, as other optional components, boron compounds, acetic acids, phosphorus compounds, alkali metals or salts thereof, antioxidants, ultraviolet absorbers, plasticizers, antistatic agents, lubricants, colorants, fillers, It may contain a heat stabilizer, another resin, a metal salt of a higher aliphatic carboxylic acid, and the like. The EVOH layer (A) may contain two or more of these components. The upper limit of the total content of these components in the EVOH layer (A) is preferably 1% by mass.

  The boron compound suppresses gelation during melt molding and suppresses torque fluctuations (viscosity change during heating) of an extruder or the like. Examples of the boron compound include boric acids such as orthoboric acid, metaboric acid, and tetraboric acid; boric acid esters such as triethyl borate and trimethyl borate; alkali metal salts or alkaline earth metal salts of the boric acids, borax And borate salts such as borohydrides. Among these, boric acids are preferable, and orthoboric acid (hereinafter also referred to as “boric acid”) is more preferable. As a minimum of content of a boron compound in EVOH layer (A), 100 ppm is preferred and 150 ppm is more preferred. Moreover, as an upper limit of content of the boron compound in EVOH layer (A), 5,000 ppm is preferable, 4,000 ppm is more preferable, and 3,000 ppm is more preferable. If the boron compound content is less than the above lower limit, torque fluctuations in an extruder or the like may not be sufficiently suppressed. On the other hand, if the content of the boron compound exceeds the above upper limit, gelation is likely to occur during melt molding, and the appearance of the multilayer body and thus the thermoformed container may be deteriorated. In addition, content of a boron compound is boron element conversion content of the boron compound in a dry resin composition.

  Acetic acids prevent coloration of the multilayer body and thus the thermoformed container, and suppress gelation during melt molding. The acetic acids include acetic acid and acetate. As acetic acid, it is preferable to use acetic acid and acetate together, and it is more preferable to use acetic acid and sodium acetate together. As a minimum of content of acetic acid in EVOH layer (A), 50 ppm is preferred, 100 ppm is more preferred, 150 ppm is still more preferred, and 200 ppm is especially preferred. Moreover, as an upper limit of content of acetic acid in EVOH layer (A), 1,000 ppm is preferable, 500 ppm is more preferable, and 400 ppm is further more preferable. If the content of acetic acid is less than the above lower limit, a sufficient anti-coloring effect cannot be obtained, and there is a possibility that yellowing may occur in the multilayer body and thus the thermoformed container. On the other hand, if the content of acetic acid exceeds the upper limit, gelation tends to occur during melt molding, particularly during long melt molding, and the appearance of the multilayer body and thus the thermoformed container may be deteriorated.

  The phosphorus compound suppresses generation and coloring of defects such as streaks and fish eyes and improves long run properties. Examples of the phosphorus compound include phosphates such as phosphoric acid and phosphorous acid. As said phosphate, any form of a primary phosphate, a secondary phosphate, and a tertiary phosphate may be sufficient. Further, the cation species of the phosphate are not particularly limited, but alkali metal salts and alkaline earth metal salts are preferable. Among these, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dihydrogen phosphate are preferable. Sodium and dipotassium hydrogen phosphate are more preferable, and sodium dihydrogen phosphate and dipotassium hydrogen phosphate are more preferable. As a minimum of content of a phosphorus compound in EVOH layer (A), 1 ppm is preferred, 2 ppm is more preferred, 3 ppm is still more preferred, and 5 ppm is especially preferred. The upper limit of the phosphorus compound content in the EVOH layer (A) is preferably 200 ppm, more preferably 150 ppm, and even more preferably 100 ppm. When the content of the phosphorus compound is less than the above lower limit or exceeds the above upper limit, the thermal stability is reduced, and there is a risk that gelled spots and coloration are likely to occur during long-time melt molding. .

  Examples of the alkali metal include lithium, sodium, potassium and the like. Examples of the alkali metal salt include monovalent metal aliphatic carboxylates, aromatic carboxylates, metal complexes, and the like. Specifically, potassium acetate, sodium salt of ethylenediaminetetraacetic acid, etc. Is mentioned. The lower limit of the alkali metal content in the EVOH layer (A) is preferably 20 ppm, and more preferably 50 ppm. Moreover, as a minimum of content of the alkali metal in EVOH layer (A), 1,000 ppm is preferable and 500 ppm is more preferable.

Examples of the antioxidant include 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4′-thiobis (6-t-butylphenol), 2,2 Examples include '-methylene-bis (4-methyl-6-tert-butylphenol), octadecyl-3- (3', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate.
Examples of the ultraviolet absorber include ethylene-2-cyano-3,3′-diphenyl acrylate, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3′-t). -Butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-oxybenzophenone and the like. .
Examples of the plasticizer include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, wax, liquid paraffin, and phosphate ester.
Examples of the antistatic agent include pentaerythritol monostearate, sorbitan monopalmitate, sulfated polyolefins, polyethylene oxide, polyethylene glycol (trade name: carbowax) and the like.
Examples of the lubricant include ethylene bisstearamide and butyl stearate.
Examples of the colorant include carbon black, phthalocyanine, quinacridone, indoline, azo pigment, and bengara.
Examples of the filler include glass fiber, wollastonite, calcium silicate, talc, and montmorillonite.
Examples of the heat stabilizer include hindered phenol compounds and hindered amine compounds.
Examples of other resins include polyamide and polyolefin.
Examples of the metal salt of the higher aliphatic carboxylic acid include sodium stearate, potassium stearate, calcium stearate, magnesium stearate and the like.

  In addition, as a countermeasure against gelation, for example, hindered phenol compounds and hindered amine compounds exemplified as the heat stabilizer, metal salts of the higher fatty acid carboxylic acids, hydrotalcite compounds, and the like may be added. These may be used alone or in combination of two or more. The lower limit of the addition amount of the compound for preventing gelation is usually 0.01% by mass with respect to the EVOH layer (A). Moreover, the upper limit of the addition amount of the compound for a gelatinization countermeasure is 1 mass% normally with respect to EVOH layer (A).

  Although it does not specifically limit as a minimum of the average thickness of EVOH layer (A), From viewpoints, such as barrier property and mechanical strength, 0.02% is preferable with respect to whole average thickness, 0.5% Is more preferable, 1.0% is further more preferable, and 1.5% is particularly preferable. Further, the upper limit of the average thickness of the EVOH layer (A) is not particularly limited, but is preferably 34% and more preferably 5% with respect to the overall average thickness from the viewpoint of barrier properties and mechanical strength. Preferably, 4.5% is more preferable. The lower limit of the average thickness of the EVOH layer (A) is, for example, 2 μm. Moreover, as an upper limit of the average thickness of EVOH layer (A), it is 100 micrometers, for example.

<Method for Producing EVOH Layer (A)>
The EVOH layer (A) can be formed, for example, by extruding an EVOH-containing resin composition containing EVOH (I) and unsaturated aldehyde (II).

[Method for preparing EVOH-containing resin composition]
EVOH-containing resin composition is a production method in which unsaturated aldehyde (II) can be uniformly blended in EVOH (I), and 0.01 to 100 ppm of unsaturated aldehyde (II) is contained in EVOH layer (A) If it is, it will not specifically limit. Examples of a method for preparing an EVOH-containing resin composition (hereinafter also referred to as “resin composition”) include: (1) a step of copolymerizing ethylene and vinyl ester; and (2) a copolymer obtained by step (1). It can be obtained by a production method including a step of saponifying a polymer.

The method for containing a specific amount of unsaturated aldehyde (II) in the resin composition is not particularly limited. For example, a method of adding a specific amount of unsaturated aldehyde (II) in the step (1),
A method of adding a specific amount of unsaturated aldehyde (II) in the step (2),
The method etc. which add specific amount unsaturated aldehyde (II) to EVOH (I) obtained by the said process (2) are mentioned. However, if a method of adding a specific amount of unsaturated aldehyde (II) in the step (1) or a method of adding a specific amount of unsaturated aldehyde (II) in the step (2) is adopted, In order to contain the desired amount of unsaturated aldehyde (II) in the resin composition to be added, the amount added in consideration of the amount consumed in the polymerization reaction in step (1) and the saponification reaction in step (2) Need to be more. Therefore, when adding unsaturated aldehyde (II) at a polymerization reaction or a saponification reaction process, it is preferable to add and add the amount of unsaturated aldehyde (II) consumed. On the other hand, the method of adding a specific amount of unsaturated aldehyde (II) to EVOH (I) obtained from the above step (2) is excellent in operability because it can be added without considering consumption within the step. .

  As a method of adding a specific amount of unsaturated aldehyde (II) to EVOH (I), for example, a method of previously blending unsaturated aldehyde (II) with EVOH (I) and granulating pellets, ethylene-vinyl ester Method for impregnating unsaturated aldehyde (II) in strands precipitated in step of depositing paste after saponification of polymer, method for impregnating unsaturated aldehyde (II) after cutting the precipitated strand, and dry resin composition A method of adding unsaturated aldehyde (II) to a redissolved chip, a method of melt-kneading a blend of two components of EVOH (I) and unsaturated aldehyde (II), EVOH melting from the middle of the extruder A method of feeding unsaturated aldehyde (II) into a product and containing unsaturated aldehyde (II) as a part of EVOH (I) High concentrations by blending to create a master batch was granulated EVOH (I) and a method in which melt-kneading the dry blend can be mentioned.

  Among these, from the viewpoint that a small amount of unsaturated aldehyde (II) can be uniformly dispersed in EVOH (I), as the unsaturated aldehyde (II) mixing step, unsaturated aldehyde (II) is previously converted to EVOH ( It is preferable to be a step of blending with I) and granulating the pellet. Specifically, an unsaturated aldehyde (II) is added to a solution obtained by dissolving the resin composition in a good solvent such as a water / methanol mixed solvent, and the mixed solution is extruded into a poor solvent from a nozzle or the like to precipitate and By pelletizing and / or coagulating, pellets in which the unsaturated aldehyde (II) is uniformly mixed with the resin composition can be obtained.

  Moreover, unsaturated aldehyde (II) can also be added simultaneously with conjugated polyene compound (III) in the post process of a superposition | polymerization process. By adding at the same time as the conjugated polyene compound (III), the auxiliary function of the conjugated polyene compound (III) is exhibited, and the production of a substance that is difficult to be thermally melted is suppressed. As a result, a film having an excellent appearance can be obtained.

  Examples of the method of adding each component other than the unsaturated aldehyde (II) to the EVOH layer (A) include, for example, a method of mixing and melting and kneading the pellets together with the components, and an unsaturated aldehyde when preparing the pellets. Examples include a method of mixing each component together with (II), a method of immersing the pellet in a solution containing each component, and the like. For mixing each component, a ribbon blender, a high speed mixer kneader, a mixing roll, an extruder, an intensive mixer, or the like can be used.

<Thermoplastic resin layer (B)>
The thermoplastic resin layer (B) is a layer containing a thermoplastic resin other than EVOH (I). As the thermoplastic resin, a thermoplastic resin having a solubility parameter calculated from the Fedors equation of 11 or less (cal / cm ³ ) ^1/2 is preferable.

  Although it does not specifically limit as a thermoplastic resin contained in a thermoplastic resin layer (B), For example, polyethylene (linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene etc.), ethylene-vinyl acetate Copolymer, ethylene-propylene copolymer, polypropylene, copolymer of propylene and α-olefin having 4 to 20 carbon atoms, homopolymer or copolymer of olefin such as polybutene and polypentene, polystyrene, polyvinyl chloride , Polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, chlorinated polypropylene, and the like. Among these, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polypropylene, and polystyrene are preferable, and high-density polyethylene is more preferable.

The lower limit of the density of the high-density polyethylene is preferably 0.93 g / cm ^{3 and} more preferably 0.95 g / cm ³ from the viewpoints of rigidity, impact resistance, moldability, drawdown resistance, gasoline resistance, and the like. 0.96 g / cm ³ is more preferable. The upper limit of the density of the high-density polyethylene is preferably 0.98 g / cm ³ from the viewpoints of rigidity, impact resistance, moldability, drawdown resistance, gasoline resistance, and the like. Further, the lower limit of the melt flow rate (MFR) of the high-density polyethylene is preferably 0.01 g / 10 min at 190 ° C. under a load of 2,160 g. Further, the upper limit of the melt flow rate (MFR) of the high-density polyethylene is preferably 0.5 g / 10 minutes, more preferably 0.1 g / 10 minutes under a load of 190 ° C. and 2,160 g.

  The high-density polyethylene can be appropriately selected from commercially available products. In addition, the thermoplastic resin layer (B) may contain other optional components similar to those of the EVOH layer (A) as long as the effects of the present invention are not impaired. Examples of other optional components include a colorant that may be contained in the EVOH layer.

  Although it does not specifically limit as a minimum of the average thickness of a thermoplastic resin layer (B), From viewpoints, such as mechanical strength, 0.05% is preferable with respect to the whole average thickness. The upper limit of the average thickness of the thermoplastic resin layer (B) is not particularly limited, but is preferably 15% with respect to the overall average thickness from the viewpoint of mechanical strength and the like. The lower limit of the average thickness of the thermoplastic resin (B) is, for example, 5 μm. Moreover, as an upper limit of the average thickness of a thermoplastic resin (B), it is 1000 micrometers, for example.

<Polyolefin layer (C)>
The polyolefin layer (C) is a layer mainly composed of a carboxylic acid-modified polyolefin. The polyolefin layer (C) can function as an adhesive layer between the EVOH layer (A) and the thermoplastic resin layer (B). The carboxylic acid-modified polyolefin is a carboxyl group or an anhydride group obtained by chemically bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an olefin polymer by an addition reaction, a graft reaction or the like. An olefin polymer having

  Examples of the ethylenically unsaturated carboxylic acid or anhydride thereof include monocarboxylic acid, monocarboxylic acid ester, dicarboxylic acid, dicarboxylic acid monoester, dicarboxylic acid diester, and dicarboxylic acid anhydride. Specifically, as the ethylenically unsaturated carboxylic acid or its anhydride, maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, maleic acid monomethyl ester, maleic acid monoethyl ester, maleic acid diethyl ester And fumaric acid monomethyl ester. Among these, dicarboxylic anhydrides such as maleic anhydride and itaconic anhydride are preferable, and maleic anhydride is more preferable.

Examples of the olefin polymer include polyolefins such as low density, medium density or high density polyethylene, linear low density polyethylene, polypropylene, and bolibene;
Olefin-vinyl ester copolymers such as ethylene-vinyl acetate copolymer and ethylene-ethyl acrylate copolymer;
And a copolymer of an olefin and a comonomer such as an unsaturated carboxylic acid ester. Among these, linear low density polyethylene, ethylene-vinyl acetate copolymer having a vinyl acetate content of 5% to 55% by mass, and ethylene-acrylic acid having an ethyl acrylate content of 8% to 35% by mass. Ethyl copolymers are preferred, linear low density polyethylene, and ethylene-vinyl acetate copolymers having a vinyl acetate content of 5% to 55% by weight are more preferred.

  Carboxylic acid-modified polyolefin, for example, by introducing an ethylenically unsaturated carboxylic acid or its anhydride into an olefin polymer in the presence of a solvent such as xylene or a catalyst such as peroxide by an addition reaction or a graft reaction. Is obtained. At this time, the lower limit of the amount of carboxylic acid or its anhydride added to the olefin polymer or the graft amount (modification degree) is preferably 0.01% by mass relative to the olefin polymer, and 0.02% by mass. Is more preferable. Moreover, as an upper limit of the addition amount to the olefin polymer of the said carboxylic acid or its anhydride, or the graft amount (modification degree), 15 mass% is preferable and 10 mass% is more preferable. Carboxylic acid modified polyolefin may use 1 type, or may mix and use 2 or more types. The polyolefin layer (C) may contain other optional components similar to those of the EVOH layer (A) in addition to the carboxylic acid-modified polyolefin within a range not impairing the effects of the present invention.

  The lower limit of the average thickness of the polyolefin layer (C) is not particularly limited, but is preferably 0.3%, more preferably 0.6%, and further 1.2% with respect to the overall average thickness. preferable. The upper limit of the average thickness of the polyolefin layer (C) is not particularly limited, but is preferably 12% and more preferably 9% with respect to the overall average thickness. There exists a possibility that adhesiveness may fall that the thickness of a polyolefin layer (C) is less than the said minimum. On the other hand, if the thickness of the polyolefin layer (C) exceeds the above upper limit, the cost may increase. As a minimum of average thickness of polyolefin layer (C), it is 2 micrometers, for example. Moreover, as an upper limit of the average thickness of a polyolefin layer (C), it is 100 micrometers, for example.

<Recovery layer (D)>
The recovery layer (D) is a layer formed using a recovered material of at least one of the EVOH layer (A), the thermoplastic resin layer (B), and the polyolefin layer (C) in the manufacturing process of the thermoformed container. It is. The recovery layer (D) comprises at least one of EVOH (I), a thermoplastic resin having a solubility parameter calculated from the formula of Fedors of 11 (cal / cm ³ ) ^1/2 or less, and a carboxylic acid-modified polyolefin. contains. In addition, the recovery layer (D) is formed by using the EVOH layer (A), the thermoplastic resin layer (B) and the polyolefin layer (C) recovered in the manufacturing process of the thermoformed container, rejected products of the test, and the like. The By providing the recovery layer (D) that reuses such scraps and the like, it is possible to reduce the loss of the resin used when manufacturing the thermoformed container and to reduce the cost.

  The recovery layer (D) can be used as a substitute for the thermoplastic resin layer (B), but generally the mechanical strength of the recovery layer (D) is lower than that of the thermoplastic resin layer (B). In many cases, the recovery layer (D) is preferably used by being laminated with the thermoplastic resin layer (B). Such a recovery layer (D) is preferably arranged so as to be closer to the outer surface side of the accommodating portion than the EVOH layer (A). This is because when the thermoformed container receives an impact from the outside, stress concentration occurs in the thermoformed container, and the compressive stress with respect to the impact works on the container inner layer side (the inner surface side of the accommodating part) in the stress concentration part, This is because damage may occur. Further, the recovery layer (D) may be disposed on both sides of the EVOH layer (A) when a large amount of resin needs to be recycled, such as when a large amount of scrap is generated.

  The upper limit of the EVOH (I) content in the recovery layer (D) is preferably 9.0% by mass. When the content of EVOH (I) in the recovery layer (D) exceeds 9.0% by mass, cracks tend to occur at the interface with the thermoplastic resin layer (B), and the entire thermoformed container starts from the cracks. There is a risk of destruction.

<Method for producing multilayer body>
The multilayer body can be formed using a coextrusion molding apparatus. This multilayer body includes, for example, a resin composition that forms an EVOH layer (A), a resin composition that forms a thermoplastic resin layer (B), a resin composition that forms a polyolefin layer (C), and a recovery layer (D). The resin composition and the like to be formed are charged into separate extruders and coextruded with these extruders to form a predetermined layer structure.

  The extrusion of each layer is performed by operating an extruder equipped with a single screw or a twin screw at a predetermined temperature. As a minimum of the temperature of the extruder which forms EVOH layer (A), it is 170 ° C, for example. Moreover, as an upper limit of the temperature of the extruder which forms EVOH layer (A), it is 210 degreeC, for example. As a minimum of the temperature of the extruder which forms a thermoplastic resin layer (B), it is 200 degreeC, for example. Moreover, as an upper limit of the temperature of the extruder which forms a thermoplastic resin layer (B), it is 240 degreeC, for example. The lower limit of the temperature of the extruder for forming the polyolefin layer (C) is, for example, 160 ° C. Moreover, as an upper limit of the temperature of the extruder which forms a polyolefin layer (C), it is 220 degreeC, for example. As a minimum of the temperature of the extruder which forms a recovery layer (D), it is 200 ° C, for example. Moreover, as an upper limit of the temperature of the extruder which forms a collection layer (D), it is 240 degreeC, for example.

<Thermoforming>
The thermoformed container can be formed by heating and softening a multilayer body such as a film or a sheet, and then molding it into a mold shape. As thermoforming methods, for example, vacuum or compressed air is used, and if necessary, a plug is used to mold into a mold shape (straight method, drape method, air slip method, snapback method, plug assist method, etc.), press molding And the like. Various molding conditions such as molding temperature, degree of vacuum, pressure of compressed air, molding speed, and the like are appropriately set depending on the plug shape, mold shape, raw material film and sheet properties, and the like. The molding temperature is not particularly limited as long as the resin can be softened enough to be molded, and the suitable temperature range varies depending on the configuration of the multilayer body such as a film or sheet.

  When the film is thermoformed, it should not be so high that melting of the film due to heating or unevenness of the metal surface of the heater plate is transferred to the film, but not so low that shaping is not sufficient, The lower limit of the specific film temperature is usually 50 ° C, preferably 60 ° C, and more preferably 70 ° C. Moreover, as an upper limit of the said film temperature, it is 120 degreeC normally, 110 degreeC is preferable and 100 degreeC is more preferable.

  On the other hand, when a sheet is thermoformed, it may be possible to mold at a higher temperature than in the case of a film. In this case, the lower limit of the sheet temperature is 130 ° C., for example. Moreover, as an upper limit of the said sheet | seat temperature, it is 180 degreeC, for example.

  The thermoforming container has a step of thermoforming using a resin composition containing EVOH (I) as a main component, and the resin composition contains unsaturated aldehyde (II), and this unsaturated aldehyde (II) It is preferable to manufacture by the manufacturing method whose content in the said resin composition is 0.05 ppm or more and 50 ppm or less. As a minimum of content in unsaturated resin (II) in the above-mentioned resin composition, 0.1 ppm is preferred and 0.15 ppm is more preferred. Moreover, as an upper limit of content in unsaturated resin (II) in the said resin composition, 30 ppm is preferable and 20 ppm is more preferable.

<Layer structure>
The thermoformed container of the present invention only needs to have at least the EVOH layer (A), and may be composed of a single layer or a plurality of layers. What is necessary is just to set the layer structure in case a thermoforming container is multiple layers according to a use etc. suitably.

As a layer structure in the case where the thermoformed container is composed of a plurality of layers, it is preferable to arrange the thermoplastic resin layer (B) in the outermost layer. That is, from the inner surface to the outer surface of the housing portion, the thermoplastic resin layer (B) / polyolefin layer (C) / EVOH layer (A) / polyolefin layer (C) / thermoplastic resin layer (B) (hereinafter, "(Inner surface) (B) / (C) / (A) / (C) / (B) (outer surface)") is preferable from the viewpoint of impact resistance. Moreover, as a layer structure in the case of including a collection layer (D), for example, (inner surface) (B) / (C) / (A) / (C) / (D) / (B) (outer surface),
(Inner surface) (B) / (D) / (C) / (A) / (C) / (B) (outer surface),
(Inner surface) (B) / (D) / (C) / (A) / (C) / (D) / (B) (outer surface),
(Inner surface) (D) / (C) / (A) / (C) / (D) (outer surface) and the like. In these layer structures, a recovery layer (instead of the thermoplastic resin (B) layer) D) may be used. Among these, (inner surface) (B) / (C) / (A) / (C) / (D) / (B) (outer surface), (inner surface) (B) / (D) / (C ) / (A) / (C) / (D) / (B) (outer surface). When a plurality of layers (A) to (D) are used, the resins constituting each layer may be the same or different.

<Cup container>
Next, the thermoformed container of the present invention will be specifically described taking the cup-shaped container shown in FIGS. 1 and 2 as an example. However, the cup-shaped container is only an example of a thermoformed container, and the following description of the cup-shaped container does not limit the scope of the present invention.

  The cup-shaped container 1 of FIG.1 and FIG.2 is provided with the cup main body 10 and the flange part 11 as an accommodating part. The cup-shaped container 1 is used by accommodating the contents in the cup body 10 and sealing the lid 2 on the flange portion 11 so as to close the opening 12 of the cup body 10. Examples of the seal include a resin film, a metal foil, a metal resin composite film, and the like. Among these, a metal resin composite film in which a metal layer is laminated on the resin film is preferable. Examples of the resin film include a polyethylene film and a polyethylene terephthalate film. Although it does not specifically limit as a metal layer, Metal foil and a metal vapor deposition layer are preferable, and aluminum foil is more preferable from a viewpoint of gas barrier property and productivity.

  The cup-shaped container 1 can be obtained by thermoforming a multilayer body such as a film or sheet. This multilayer body preferably includes an EVOH layer (A), and other layers are laminated on the EVOH layer (A). Examples of the other layers include a thermoplastic resin layer (B), a polyolefin layer (C), and a recovery layer (D).

  As a layer structure of the cup-shaped container 1, the structure shown in FIG. 3 is preferable. In the illustrated layer configuration, the thermoplastic resin layer (B) 10B is laminated on one surface side of the EVOH layer (A) 10A (the inner surface 13 side of the cup body 10 of the cup 1) via the polyolefin layer (C) 10C. The recovery layer (D) 10D and the thermoplastic resin layer (B) 10B are laminated on the other surface side (the outer surface 14 side of the cup body 10 of the cup 1) via the polyolefin layer (C) 10C. is there.

<Method for producing cup-shaped container>
As shown in FIG. 4, the cup-shaped container 1 is manufactured by heating and softening a continuous multilayer body 3 such as a film or sheet using a heating device 4 and then thermoforming using a mold device 5. The

(Heating device)
The heating device 4 includes a pair of heaters 40 and 41, and the continuous multilayer body 3 can pass between the heaters 40 and 41. In addition, as the heating apparatus 4, what is heated by hot press can also be used.

(Molding equipment)
The mold apparatus 5 is suitable for thermoforming by the plug assist method, and includes a lower mold 50 and an upper mold 51 accommodated in a chamber (not shown). The lower mold 50 and the upper mold 51 are individually movable in the vertical direction, and the continuous multilayer body 3 can pass between the lower mold 50 and the upper mold 51 in the separated state. The lower mold 50 has a plurality of recesses 52 for forming the accommodating portion 10 of the thermoforming container 1. The upper mold 51 includes a plurality of plugs 53 that protrude toward the lower mold 51. The plurality of plugs 53 are provided at positions corresponding to the plurality of recesses 52 of the lower mold 50. Each plug 53 can be inserted into the corresponding recess 52.

(Thermoforming)
First, as shown in FIG. 5 (A), the continuous multilayer body 3 softened by the heating device 4 is brought into close contact with the lower mold 50 by moving the lower mold 50 upward, and the continuous multilayer body 3 is slightly lifted. Then, tension is applied to the continuous multilayer body 3. Next, as shown in FIG. 5B, the plug 53 is inserted into the recess 52 by moving the upper mold 51 downward.

  Subsequently, as shown in FIG. 5C, the upper mold 51 is moved upward to separate the plug 53 from the recess 52, and then the inside of the chamber (not shown) is evacuated, and the continuous multilayer body 3 is removed from the recess 52. Adhere to the inner surface. Then, the shape is fixed by cooling the molding part by air injection. As shown in FIG. 5D, the chamber (not shown) is opened to the atmosphere, and the lower mold 50 is moved downward to release the lower mold 50 to obtain a primary molded product. By cutting this primary molded product, the cup-shaped container 1 shown in FIGS. 1 and 2 is obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In the following, “%” and “part” represent “% by mass” and “part by mass”, respectively, unless otherwise specified.

<Synthesis of EVOH>
[Synthesis Example 1]
Polymerization was carried out under the following conditions using a 250 L pressurized reaction tank to synthesize an ethylene-vinyl acetate copolymer.

(Preparation amount)
Vinyl acetate 83.0kg
26.6 kg of methanol
Feed rate of 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile) (2.5 g / L methanol solution) 1119.5 mL / hr

(Polymerization conditions)
Polymerization temperature 60 ° C
Polymerization tank ethylene pressure 3.6 MPa
Polymerization time 5.0 hours

  The polymerization rate of vinyl acetate in the obtained copolymer was about 40%. After adding sorbic acid to this copolymerization reaction solution, the sorbic acid is supplied to the extraction tower, and unreacted vinyl acetate is removed from the top of the tower by introducing methanol vapor from the bottom of the tower. % Methanol solution was obtained. The ethylene content of this ethylene-vinyl acetate copolymer was 32 mol%. This methanol solution of ethylene-vinyl acetate copolymer is charged into a saponification reactor, and caustic soda / methanol solution (80 g / L) is added to 0.4 equivalent to the vinyl ester component in the copolymer. , Methanol was added to adjust the copolymer concentration to 20%. This solution was heated to 60 ° C. and reacted for about 4 hours while blowing nitrogen gas into the reactor. This solution was extruded into water from a metal plate having a circular opening, precipitated, and cut to obtain pellets having a diameter of about 3 mm and a length of about 5 mm. The obtained pellet was drained with a centrifuge, and the operation of adding a large amount of water and draining was repeated.

[Synthesis Example 2]
A pellet was obtained in the same manner as in Synthesis Example 1 except that sorbic acid and crotonaldehyde were added simultaneously in Synthesis Example 1.

<Example 1>
[Preparation of EVOH-containing resin composition]
20 kg of the lysed pellets obtained in Synthesis Example 1 were placed in 180 kg of a mixed solvent of water / methanol = 40/60 (mass ratio) and stirred at 60 ° C. for 6 hours to completely dissolve the pellets. Crotonaldehyde and sorbic acid as a conjugated polyene compound (III) were added to the obtained solution, and the mixture was further stirred for 1 hour to completely dissolve crotonaldehyde and sorbic acid to obtain a resin composition solution. This resin composition solution was continuously extruded from a nozzle having a diameter of 4 mm into a coagulation bath of water / methanol = 90/10 (mass ratio) adjusted to 0 ° C. to be solidified into a strand. This strand was introduced into a pelletizer to obtain a porous resin composition chip. The obtained porous resin composition chip was washed with an acetic acid aqueous solution and ion-exchanged water. The cleaning liquid and the resin composition chip are separated and drained, and then placed in a hot air dryer, dried at 80 ° C. for 4 hours, and further dried at 100 ° C. for 16 hours to obtain a resin composition (dried resin composition). Pellets).

[Production of coextrusion film formation]
Using a coextrusion molding apparatus, a homopolypropylene ("PY220" manufactured by Mitsubishi Noblen Co., Ltd.) that forms the thermoplastic resin layer (B), an EVOH resin composition that forms the EVOH layer (A), and a polyolefin layer (C) are formed. Carboxylic acid-modified polyolefin (“QF-500” manufactured by Mitsui Chemicals Admer Co., Ltd.) and a resin mixture for forming a recovery layer (D) were charged into separate extruders, and (B): 425 μm / (C): 50 μm / ( A multilayer sheet having a layer structure of A): 50 μm / (C): 50 μm / (D): 250 μm / (B): 425 μm and a total layer thickness of 1250 μm was produced. For extrusion, homopolypropylene is 65 mm in diameter, and an extruder equipped with a single screw of L / D = 22 is set to a temperature of 200 ° C. to 240 ° C., and the EVOH resin composition is a single screw of 40 mm in diameter and L / D = 26. The extruder equipped with a screw is set to a temperature of 170 ° C. to 210 ° C., the carboxylic acid-modified polyolefin is set to a temperature of 160 ° C. to 220 ° C. for an extruder equipped with a single screw having a diameter of 40 mm and L / D = 26, and a recovery layer The resin mixture of (D) is a twin-screw extruder (“2D25W” manufactured by Toyo Seiki Seisakusho, diameter 25 mm, screw rotation speed 100 rpm) with a temperature of 220 ° C. and a feed block die (width 600 mm) 255. It was carried out by operating at 0 ° C.

  In addition, the resin mixture for forming a collection | recovery layer (D) was prepared as follows. 6.7 parts by mass of an EVOH resin composition forming the EVOH layer (A), 88.3 parts by mass of homopolypropylene ("PY220" manufactured by Mitsubishi Nobren) forming the thermoplastic resin layer (B), and an olefin layer (C After dry blending 5.0 parts by weight of carboxylic acid-modified polyolefin ("QF-500" from Mitsui Chemicals Admer), a twin-screw extruder ("2D25W" from Toyo Seiki Seisakusho, diameter 25 mm, screw rotation speed) The cylinder and die at 100 rpm) were set to a temperature of 220 ° C., and extrusion pelletization was performed in a nitrogen atmosphere to obtain pellets. The operation of mixing and removing the pellets in a twin-screw extruder under a nitrogen atmosphere was further repeated 4 times to obtain a resin mixture for forming the recovery layer (D).

[Production of thermoformed container]
The multilayer sheet obtained by the coextrusion molding apparatus is cut into a 15 cm square and is cup-shaped (die shape 70φ × 70 mm, drawing ratio) under the condition of a sheet temperature of 150 ° C. using a batch thermoforming tester manufactured by Asano Manufacturing Co., Ltd. S = 1.0) was thermoformed (pressure air: 5 kg / cm ² , plug: 45φ × 65 mm, syntax foam, plug temperature: 150 ° C., mold temperature: 70 ° C.) to prepare a thermoformed container.

<Examples 2 to 14 and Comparative Examples 1 and 2>
A multilayer sheet was prepared in the same manner as in Example 1 except that the resin composition was prepared so that the content of each component was as shown in Table 1, and a thermoformed container was formed by thermoforming the multilayer sheet. Produced.

<Comparative Example 3>
A multilayer sheet was produced in the same manner as in Example 2 except that the pellets obtained in Synthesis Example 2 were used, and a thermoformed container of Comparative Example 3 was produced by thermoforming this multilayer sheet.

<Evaluation>
For the resin compositions, multilayer sheets and thermoformed containers prepared in Examples 1-14 and Comparative Examples 1-3, the content of unsaturated aldehyde (II), conjugated polyene compound (III) Content, average thickness of EVOH layer (A), EVOH content in EVOH layer (A), odor during molding, solution appearance, motor torque fluctuation evaluation, appearance and impact resistance were evaluated. The evaluation results are shown in Table 1.

[Quantification of Unsaturated Aldehyde (II) Content]
To 200 mg of a 50% 2,4-dinitrophenylhydrazine (DNPH) solution, 50 mL of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), 11.5 mL of acetic acid and 8 mL of ion-exchanged water were added, A DNPH adjustment solution is prepared. Thereafter, 1 g of the dried resin composition pellets was added to 20 mL of the DNPH adjustment solution and dissolved by stirring at 35 ° C. for 1 hour. Acetonitrile was added to this solution to precipitate EVOH, and the solution was filtered and concentrated to obtain an extracted sample. The amount of unsaturated aldehyde (II) was quantified by quantitatively analyzing the extracted sample by high performance liquid chromatography. For quantification, a calibration curve prepared using a sample of unsaturated aldehyde (II) was used.

[Quantification of content of conjugated polyene compound (III)]
The dried resin composition pellets are pulverized by freeze pulverization, and 10 g of pulverized material obtained by removing coarse particles by a sieve having a nominal size of 0.150 mm (100 mesh) (conforming to JIS standard Z8801-1-3) is put into a Soxhlet extractor. Filled and extracted with 100 mL of chloroform for 48 hours. The amount of the conjugated polyene compound (III) in this extract was quantitatively analyzed by high performance liquid chromatography, whereby the amount of the conjugated polyene compound (III) was quantified. For quantification, a calibration curve prepared using a sample of each conjugated polyene compound (III) was used.

[Measurement of average thickness of EVOH layer (A)]
The average thickness of the EVOH layer (A) is measured by subjecting a photograph obtained by observing a cross section of a sample collected from the thermoforming container with a scanning electron microscope, and performing image processing on any of the images obtained at this time. It was calculated as a ratio (%) of the average value of the point thickness to the overall average thickness.

[Content of EVOH in EVOH Layer (A)]
The EVOH content in the EVOH layer (A) was the content in the dry resin composition used to form the EVOH layer (A).

[Odor during molding]
The odor during molding was evaluated by the following method. 20 g of the resin composition obtained by kneading with the above lab plast mill was placed in a 100 mL glass sample tube, the mouth was covered with aluminum foil, and then heated in a hot air dryer at 150 ° C. for 90 minutes. After taking out from the dryer and allowing to cool at room temperature for 1 hour, the sample tube was shaken 2-3 times, and then the lid of the aluminum foil was removed to confirm the odor. The odor intensity of the sample pellets was evaluated according to the following criteria.
A (good): No odor B (slightly good): Weak odor C (slightly bad): Obvious odor D (poor): Severe odor with irritating odor

[Evaluation of solution appearance]
10 g of EVOH pellets heat-treated at 120 ° C. in air for 15 hours were placed in a 300 mL Erlenmeyer flask, 100 mL of a water / propanol mixed solution (45/55 (mass ratio)) was added, and the mixture was dissolved by stirring at 75 ° C. for 3 hours. The appearance of the obtained solution was evaluated according to the following criteria.
(Transparency evaluation criteria)
A (good): transparent, no visible suspended matter.
B (slightly good): Slightly cloudy, with floating matter that can be visually confirmed.
C (defect): cloudiness, suspended matter.
(Solution coloring criteria)
A (good): colorless B (slightly good): slightly yellowed C (poor): markedly yellowed

[Motor torque fluctuation evaluation]
Torque change was measured when 60 g of EVOH pellets were kneaded at 100 rpm and 260 ° C. in a lab plast mill (“20R200” biaxially different from Toyo Seiki Seisakusho). The motor torque was evaluated by measuring the torque after 5 minutes from the start of kneading and measuring the time until the torque value became 1.5 times the torque after 5 minutes. The longer this time, the smaller the viscosity change and the better the long run property.
(Criteria)
A: 60 minutes or more B: 40 minutes or more and less than 60 minutes C: 20 minutes or more and less than 40 minutes

[Appearance evaluation of thermoformed containers]
About the thermoforming container shape | molded using the multilayer sheet | seat obtained 6 hours after the start-up of a coextrusion molding apparatus, the streak and coloring were visually evaluated on the following reference | standard.
(Evaluation criteria for streak)
A (good): No streak was observed.
B (slightly good): Streaks were confirmed.
C (defect): Many streaks were confirmed.
(Evaluation criteria for coloring)
A (good): colorless B (slightly good): yellowing C (poor): markedly yellowing

[Impact resistance evaluation]
250 mL of ethylene glycol was placed in a thermoformed container formed from a multilayer sheet 20 minutes, 40 minutes, and 10 hours after the start of the coextrusion molding apparatus, and the opening was a film having a three-layer structure (polyethylene 40 μm / Aluminum foil 12 μm / polyethylene terephthalate 12 μm) was heat sealed and covered. This thermoformed container was cooled at −40 ° C. for 3 days, 10 thermoformed containers were dropped from a height of 6 m so that the opening was on top, and the number of broken thermoformed containers was evaluated. The impact resistance 20 minutes after the start of the coextrusion molding apparatus is an indicator of self-purge properties.
(Evaluation criteria for impact resistance)
A (good): less than 3 B (slightly good): 3 or more and less than 6 C (defect): 6 or more

  As shown in Table 1, in the thermoformed containers of Examples 1 to 14, the occurrence of streak and coloring were suppressed and the appearance was excellent as compared with the thermoformed containers of Comparative Examples 1 to 3. In addition, the thermoformed containers of Examples 1 to 14 were excellent in impact resistance even if they were formed 20 minutes after the start-up of the coextrusion molding apparatus. The thermoforming containers of Examples 1 to 14 are gel-like bushings that reduce impact resistance in a short time from the start of the coextrusion molding apparatus by using an EVOH-containing resin composition that is excellent in self-purge properties. It was found that the occurrence of the above was suppressed.

  The thermoforming container of the present invention contains a specific amount of unsaturated aldehyde (II) in the EVOH layer (A), thereby suppressing the occurrence of defects such as gelled blisters and streaks due to melt molding and coloring. Excellent in strength and sufficient strength. Furthermore, since the EVOH layer (A) contains a specific amount of unsaturated aldehyde (II), the thermoformed container is excellent in self-purge property in the manufacturing process, and the manufacturing cost of the thermoformed container can be reduced. it can. Therefore, the thermoformed container can be used for various applications. Since the production method of the present invention uses a resin composition containing a specific amount of unsaturated aldehyde (II), the oxidation of EVOH is prevented and the long-run property (viscosity stability) is excellent.

1 Cup-shaped container 10 Cup body 10A EVOH layer (A)
10B Thermoplastic resin layer (B)
10C Polyolefin layer (C)
10D Recovery layer (D)
DESCRIPTION OF SYMBOLS 11 Flange part 12 Opening 13 Inner surface 14 Outer surface 2 Lid 3 Continuous multilayer body 4 Heating apparatus 40, 41 Heater 5 Mold apparatus 50 Lower mold 51 Upper mold 52 Recessed part 53 Plug

Claims (9)

A thermoformed container comprising an EVOH layer (A) mainly composed of an ethylene-vinyl alcohol copolymer (I),
The thermoformed container in which the EVOH layer (A) contains an unsaturated aldehyde (II) and the content of the unsaturated aldehyde (II) in the EVOH layer (A) is 0.01 ppm or more and 100 ppm or less.   The thermoformed container according to claim 1, wherein the unsaturated aldehyde (II) is an unsaturated aliphatic aldehyde.   The thermoformed container according to claim 2, wherein the unsaturated aliphatic aldehyde is crotonaldehyde, 2,4-hexadienal, 2,4,6-octatrienal, or a combination thereof. The EVOH layer (A) further contains a conjugated polyene compound (III),
The thermoformed container according to claim 1, 2 or 3, wherein the content of the conjugated polyene compound (III) in the EVOH layer (A) is 0.01 ppm or more and 1,000 ppm or less.   The thermoformed container according to claim 4, wherein the conjugated polyene compound (III) is sorbic acid, sorbate or a combination thereof. The thermoplastic resin layer (B) laminated on one surface side and the other surface side of the EVOH layer (A), respectively, and disposed between the EVOH layer (A) and the thermoplastic resin layer (B) And a polyolefin layer (C) mainly composed of a carboxylic acid-modified polyolefin,
The solubility parameter of the thermoplastic resin constituting the thermoplastic resin layer (B) calculated from the Fedors equation is 11 (cal / cm ³ ) ^1/2 or less, and any one of claims 1 to 5 The thermoformed container according to Item.   The thermoformed container according to any one of claims 1 to 6, wherein the thermoformed container is a cup-shaped container.   The thermoformed container according to any one of claims 1 to 6, wherein the thermoformed container is a tray-like container. Forming an EVOH layer (A) using a resin composition containing ethylene-vinyl alcohol copolymer (I) as a main component and containing the unsaturated aldehyde (II);
Thermoforming a layer containing the EVOH layer (A),
The manufacturing method of the thermoformed container whose content of the said unsaturated aldehyde (II) in the said resin composition is 0.01 ppm or more and 100 ppm or less.

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